This invention relates in general to MEMS (MicroElectroMechanical Systems), and in particular to a method of controlling an actuator of a microvalve.
MEMS is a class of systems that are physically small, having features with sizes in the micrometer range. These systems have both electrical and mechanical components. The term “micromachining” is commonly understood to mean the production of three-dimensional structures and moving parts of MEMS devices. MEMS originally used modified integrated circuit (computer chip) fabrication techniques (such as chemical etching) and materials (such as silicon semiconductor material) to micromachine these very small mechanical devices. Today there are many more micromachining techniques and materials available. The term “microvalve” as used in this application means a valve having features with sizes in the micrometer range, and thus by definition is at least partially formed by micromachining. The term “microvalve device” as used in this application means a device that includes a microvalve, and that may include other components. It should be noted that if components other than a microvalve are included in the microvalve device, these other components may be micromachined components or standard sized (larger) components.
Various microvalve devices have been proposed for controlling fluid flow within a fluid circuit. For example, various microvalve devices are disclosed in U.S. Pat. Nos. 6,019,437; 6,279,606 B1; 6,494,804 B1; 6,505,811 B1; 6,533,366 B1; 6,540,203 B1; and 6,637,722 B2. A typical microvalve device includes a displaceable member or valve movably supported by a body and operatively coupled to an actuator for movement between a closed position and a fully open position. When placed in the closed position, the microvalve blocks or closes a first fluid port that is normally in fluid communication with a second fluid port, thereby preventing fluid from flowing between the fluid ports. When the microvalve moves from the closed position to the fully open position, fluid is increasingly allowed to flow between the fluid ports. A normally closed microvalve is one that will go closed in the absence of an external energizing signal, such as the application of an electrical current from an electrical actuator. A normally open microvalve is open in the absence of the application of an external energizing signal.
The actuator is usually driven by voltage supplied from a power source. It would be advantageous to be able to reduce the total amount of power required to actuate the microvalve.